AS2 (some are marked AS-2) is for door and rear glass; AS1 (or AS-1) is for windshields.
AS are standard glass codes (American Standard) used by Society of Automotive Engineers (SAE, also found on many glass). The "AS1") were laminated windshields which were required to standard 70% light transmissibility & be impact resistant. "AS2" was similiar requirements, but had to pass side impact reqirements, 70% light transmissability and was tempered.
Second code, "M" is the Model Number. M20, M25, M27 are internal PPG unknown codes. .7 indicates thickness of the glass of that particular kind. M25 usually reserved for windshields while M27 side & back glass & tinted. Some have a space between digits, others do not, in other words some might be marked M20.7 or M20 7 or M207. The digit after the internal PPG code is thickness:
.6=3/16th thickness
.7=1/8th thickness
.8=1/4 thickness
The second to last codes above (26) are manufacturing plant of origin.
25 Greensburg, PA
26 Crestline, OH
27, Tipton, PA
so above glass is from Crestline, Ohio for instance.
The end codes/far right (40) are month & year (4=Apr, 0=70 ?).
DOT 18. DOT=Department Of Transportation code for PPG
PPG Industries Pittsburgh, PA
